Waters 2475, Руководство оператора, Страница: 124 / 228

3-52 Using the Detector
If you select Cancel (Shift, 0), the Method list appears.
3. When you press HOME, the method number icon has an asterisk.
Scanning spectra
Types of scanning
The detector can collect sample scans for either excitation and emission
fluorescence spectra. A zero-scan is desirable initially.
• Zero-scan – A reference scan that characterizes the fluorescence
spectrum of a solvent in the flow cell.
• Sample scan – An excitation or emission scan of an analyte in solvent
(after subtracting the zero-scan of the solvent) to provide the actual
spectrum of the sample.
The detector can measure the spectrum of a sample using the flow cell (see
page 3-64 ) for scanning procedures.
Before you begin
Before you run a spectrum scan, you need to specify the following parameters:
• λ 1 – Starting wavelength. Scanning begins at this wavelength.
• λ 2 – Ending wavelength. Scanning ends at this wavelength.
• Gain – The gain setting for the PMT. Sometimes, you must increase this
for low sample concentrations.
• Scan Type – The type of scan (excitation or emission).
• λ other – The wavelength setting of the stationary monochromator.
• Pace – Rate of scanning in nm/min. The pace value determines how fast
a scan runs and acquires data. The scan data are acquired at the highest